My DS would reject mild chedder and cheese strings, and gouda which is also mild and quite 'plasticy' in texture.
He loves mature or extra mature cheddar, brie, saint agur (blue), cream cheese (phili) and will eat a smaller amount of something like wenslydale with fruit in, recently had a cranberry one.
If Olly likes a particular fruit the fruit cheeses could be a way to tempt him to try a bite, have a browse and the cheese/deli counter rather than on the pre-pack shelves, if you can talk him into tasting on the spot that would be great too as he could have a small piece of several and choose the one he likes. If not then you could get very small amounts of a couple of different types.
Cream cheese I more often use as 'cream' on fruit, just stir it thoroughly and dollop on strawberries or mix it through raspberries or blackberries until they start to break and make it into a pink pudding. And call it pink pudding or raspberry and blackberry pudding or whatever instead of 'cheese'. Mascarpone is a good way in to cheese too.
I'm not sure what texture/flavour soy cheese has. If it is dramatically different from real cheese then perhaps don't tell him the real cheese is cheese, just introduce it as a new food called 'wensleydale' or 'brie' so he doesn't have the expectation of soy cheese in mind when he eats it. Worth a try perhaps? (yk like when someone makes you tea and you think it's coffee and it tastes awful until you're told it is tea and then it tastes fine...or is that just me?)